Methods for fabrication of thermoplastic components

ABSTRACT

A method of fabricating a thermoplastic component using inductive heating is described. The method includes positioning a plurality of induction heating coils to define a process area for the thermoplastic component, wherein the plurality of induction heating coils comprises a first set of coils and a second set of coils. The method also includes controlling a supply of electricity provided to the plurality of inductive heating coils to intermittently activate the coils. The intermittent activation is configured to facilitate prevention of electromagnetic interference between adjacent coils.

This application is a divisional application of U.S. patent applicationSer. No. 12/210,650, filed Sep. 15, 2008.

BACKGROUND

The technical field relates generally to the fabrication ofthermoplastic components, and more specifically to the heating ofthermoplastic components during fabrication.

Typically, tooling in autoclave or hot press processing is a significantheat sink that consumes substantial energy. Furthermore, the tooling mayrequire significant time to heat the composite material to itsconsolidation temperature and, after processing the composite, to coolto a temperature at which it is safe to remove the finished compositepart. Furthermore, even distribution of heat applied to the tooling andthe composite material may be difficult, especially when manufacturing alarge component.

Fabrication of thermoplastic components may include induction heating.Typically, dies or tooling for induction processing are ceramic becauseceramic is not susceptible to induction heating and, preferably, is athermal insulator (i.e., a relatively poor conductor of heat). Castceramic tools cost less to fabricate than metal tools of comparable sizeand have less thermal mass than metal tooling because they areunaffected by the induction field. Because the ceramic tooling is notsusceptible to induction heating, it is possible to embed inductionheating elements in the ceramic tooling and to heat the composite ormetal retort without significantly heating the tools. Thus, inductionheating can reduce the time required and energy consumed to fabricate apart.

While graphite or boron fibers can be heated directly by induction, mostorganic matrix composites require a susceptor in, or adjacent to, thecomposite material preform to achieve the necessary heating forconsolidation or forming. The susceptor is heated inductively andtransfers its heat principally through conduction to the preform or workpiece. Enclosed in the metal retort, the work piece does not experiencethe oscillating magnetic field resulting from the induction process. Thefield is instead absorbed in the retort sheets. Heating is by conductionfrom the retort to the work piece.

Induction focuses heating on the retort (and work piece) and eliminateswasteful, inefficient heat sinks (e.g., tooling of conventionalprocesses). Induction heating facilitates a reduction in the differencebetween the coefficients of thermal expansion of the tools and the workpiece. Furthermore, this process is energy efficient becausesignificantly higher percentages of the input energy go to heating thework piece than occurs with conventional presses. The reduced thermalmass and ability to focus the heating energy permits the operatingtemperature to be changed rapidly. Finally, the shop environment is notheated as significantly from the radiation of the large thermal mass ofa conventional press, and is a safer and more pleasant environment forthe press operators.

Fabrication of thermoplastic components may also include thermoplasticwelding. Thermoplastic welding, which can eliminate mechanicalfasteners, features the ability to join thermoplastic compositecomponents at high speeds with minimum touch labor and little, if any,pretreatments.

Large scale parts such as wing spars and ribs, and the wing skins thatare bonded to the spars and ribs, and/or fuselage sections and supportstructure may be typically on the order of twenty to thirty feet long,and potentially can be hundreds of feet in length when the process isperfected for commercial transport aircraft. Parts of this size aredifficult to produce with perfect flatness. Instead, the typical partmay have various combinations of inconsistencies beyond designtolerance. Applying heat to the interface by electrically heating thesusceptor in connection with pressure on the parts tends to flatten theinconsistencies, but the time needed to achieve full intimate contactwith the use of heat and pressure may be excessive, and can lead toundesirable results.

An existing solution for increasing the rate of production ofthermoplastic components is to build more autoclaves and rate toolingwhen a critical rate of the current tools is reached, or to cap theproduction capabilities of a manufacturing facility at a certain ratethat does not require building new tooling. The existing autoclave basedsystems have an inherent limit at which production rates above thatcritical rate will trigger a large increment of capital expenditures tobe incurred along with a lag time required to obtain the capital,install the equipment, and ensure the equipment is functional.

Accordingly, there is a need for an apparatus and a system thatfacilitates rapid fabrication of large thermoplastic components, as wellas a related method.

SUMMARY

In one aspect, a method of fabricating a thermoplastic component usinginductive heating is provided. The method includes positioning aplurality of induction heating coils to define a process area for thethermoplastic component, wherein the plurality of induction heatingcoils comprises a first set of coils and a second set of coils. Themethod also includes controlling a supply of electricity provided to theplurality of inductive heating coils to intermittently activate thecoils. The intermittent activation is configured to facilitateprevention of electromagnetic interference between adjacent coils.

In another aspect, an inductive heating apparatus for fabricating athermoplastic component is provided. The apparatus includes a first setof induction coils and a second set of induction coils. The first andsecond sets of induction coils are positioned to define a process areafor the thermoplastic component, wherein individual coils of the firstset of induction coils alternate with individual coils of the second setof induction coils along a length of the process area. The apparatusalso includes a first power supply and a second power supply. The firstpower supply is coupled to the first set of induction coils, and thesecond power supply is coupled to the second set of induction coils.Furthermore, the first and second power supplies are configured toalternatively supply electricity to the first set of induction coils andthe second set of induction coils.

In yet another aspect, a system for fabricating a thermoplasticcomponent using induction heating is provided. The system includes athermoplastic composite preform and a susceptor. The system alsoincludes a first set of induction coils and a second set of inductioncoils positioned adjacent to the thermoplastic preform. Individual coilsof the first set of induction coils are positioned to alternate withindividual coils of the second set of induction coils to define athermoplastic component process area. The system also includes a firstpower supply and a second power supply. The first power supply iscoupled to the first set of induction coils, and the second power supplycoupled to the second set of induction coils. The first and second powersupplies are configured to alternately power the first set of inductioncoils and the second set of induction coils.

In yet another aspect, a method for fabricating a thermoplasticcomponent using inductive heating is provided. The method is for use inaircraft manufacturing. The method includes positioning at least a firstset of coils and a second set of coils to define a process area for thethermoplastic component. The coils of the first set of coils and coilsof the second set of coils alternate along a length of the process area.The method also includes configuring a first power supply to provideelectricity to coils of the first set of coils and configuring a secondpower supply to provide electricity to coils of the second set of coils.The first power supply is configured to provide electricity to coils ofthe first set of coils when the second power supply is not providingelectricity to coils of the second set of coils, and the second powersupply is configured to provide electricity to coils of the second setof coils when the first power supply is not providing electricity tocoils of the first set of coils.

In yet another aspect, an inductive heating apparatus for fabricatingthermoplastic aircraft components is provided. The apparatus includes afirst set of induction coils made up of a plurality of individual coilsegments that include at least one winding and a coil element. The firstset of induction coils are coupled to a first power supply. Theapparatus also includes a second set of induction coils made up of aplurality of individual coil segments that include at least one windingand a coil element. The first and the second set of induction coils arepositioned to define a process area for the thermoplastic component. Thecoils of the first set of induction coils and the coils of the secondset of induction coils alternate along a length of the process area. Thesecond set of induction coils is coupled to a second power supply. Thefirst power supply is configured to provide the first set of inductioncoils with electricity for a predetermined period of time while thesecond power supply is not supplying electricity to the second set ofinduction coils. Also, the second power supply is configured to providethe second set of induction coils with electricity for a predeterminedperiod of time when the first power supply is not providing electricityto the first set of induction coils.

Accordingly, there is a need for an apparatus and a system thatfacilitates rapid fabrication of large thermoplastic components, as wellas a related method.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of an exemplary wind turbine blade.

FIG. 2 is a flow diagram of aircraft production and service methodology.

FIG. 3 is a block diagram of an aircraft.

FIG. 4 is a diagram of an exemplary system for production ofthermoplastic components using induction heating.

FIG. 5 is a block diagram of a work piece positioned within a processarea.

FIG. 6 is an expanded diagram of a portion of the exemplary embodimentof the system shown in FIG. 4.

FIG. 7 is another expanded diagram of the portion of the exemplaryembodiment of the system shown in FIG. 4.

FIG. 8 is a flowchart illustrating an exemplary method for production ofthermoplastic components using induction heating.

DETAILED DESCRIPTION

In a known embodiment, induction heating for consolidating and/orforming organic matrix composite materials includes placing athermoplastic organic matrix composite preform within a metal susceptorenvelope (i.e., a retort). The thermoplastic organic matrix may be, butis not limited to, a polyarylether-ether-kctonc (PEEK) matrix material,or from a family of polymidc thermoplastic resins known as Ultem® (Ultemis a trademark of SABIC Innovative Plastics IP BV). The susceptorfacesheets of the retort are inductively heated to heat the preform. Aconsolidation and forming pressure may be applied to consolidate and, ifapplicable, to form the preform at its consolidation temperature. Ifdesired, the sealed susceptor sheets form a pressure zone. The pressurezone may be evacuated in the retort in a manner analogous toconventional vacuum bag processes for resin consolidation or, for lowvolatiles resins, like Ultem, the pressure zone can be pressurized toenhance consolidation. The retort is placed in an induction heatingpress on the forming surfaces of dies having the desired shape of themolded composite part. After the retort, the preform may be inductivelyheated to the desired elevated temperature and a differential pressuremay be applied (while maintaining the vacuum in the pressure zone aroundthe preform) across the retort. The retort functions as a diaphragm inthe press to form the preform against the die and into the desiredshape.

A variety of manufacturing operations may be performed in an inductionheating press. Each operation may have an optimum operating temperature.By way of example, and in a way not meant to limit the scope of thedisclosure, optimum operating temperatures provided to the preform bythe induction heating press may range from about 350° F. (175° C.) toabout 1950° F. (1066° C.). For each operation, the temperature usuallyneeds to be held relatively constant for several minutes to severalhours while the operations are completed. While temperature control canbe achieved by controlling the input power fed to the induction coil, aCurie temperature of the susceptor material can be used to control thetemperature applied to the preform. Proper selection of the metal oralloy in the retort's susceptor facesheets facilitates avoidingexcessive heating of the work piece irrespective of the input power.Improved control and temperature uniformity in the work piecefacilitates consistent production of work pieces. The Curie temperaturephenomenon is used to control the absolute temperature of the workpiece, and to obtain substantial thermal uniformity in the work piece,by matching the Curie temperature of the susceptor to the desiredtemperature of the induction heating operation being performed.

Rapid heating of an entire weld area during the processing of athermoplastic component would facilitate increased efficiency ofthermoplastic component production. Rapid heating results in quickmelting of the entire surface of the joint to be welded. The componentsbeing joined are then brought together and joined, which facilitatesreducing fit-up issues and allows squeeze out to bring the entirestructure into a dimensionally accurate condition.

However, to process a large thermoplastic composite component, largeinduction heating coils, of a size large enough to process thethermoplastic composite component, or multiple induction heating coilspositioned to define a process area large enough to process thecomponent, high voltage levels are required that may not be practical.To lower the voltage demand, electromagnetic fields may be supplied tothe work piece using a plurality of smaller heating coils, and bysupplying power to those coils using a plurality of power supplies.

FIG. 1 is an illustration of an exemplary wind turbine blade 10. Typicalwind turbine blades 10 may extend to over forty meters in length. Themethods and systems described herein may be used to fabricate windturbine blade 10, as well as any thermoplastic component. Large aircraftcomponents may also be fabricated from thermoplastic materials. Forexample, but not limited to, thermoplastic wings, fuselage sections,doors, control surfaces, and empennage sections are desirable. Due todemand, as well as to ensure efficient production, it is desirable toproduce thermoplastic components at a high rate. There is additionalemphasis on the use of thermoplastic materials in high rate productioncomponents due to the recycling capability of thermoplastic materials.

Referring more particularly to the drawings, embodiments of thedisclosure may be described in the context of an aircraft manufacturingand service method 100 as shown in FIG. 2 and an aircraft 102 as shownin FIG. 3. During pre-production, exemplary method 100 may includespecification and design 104 of the aircraft 102 and materialprocurement 106. During production, component and subassemblymanufacturing 108 and system integration 110 of the aircraft 102 takesplace. Thereafter, the aircraft 102 may go through certification anddelivery 112 in order to be placed in service 114. While in service by acustomer, the aircraft 102 is scheduled for routine maintenance andservice 116 (which may also include modification, reconfiguration,refurbishment, and so on).

Each of the processes of method 100 may be performed or carried out by asystem integrator, a third party, and/or an operator (e.g., a customer).For the purposes of this description, a system integrator may includewithout limitation any number of aircraft manufacturers and major-systemsubcontractors; a third party may include without limitation any numberof venders, subcontractors, and suppliers; and an operator may be anairline, leasing company, military entity, service organization, and soon.

As shown in FIG. 3, the aircraft 102 produced by exemplary method 100may include an airframe 118 with a plurality of systems 120 and aninterior 122. Examples of high-level systems 120 include one or more ofa propulsion system 124, an electrical system 126, a hydraulic system128, and an environmental system 130. Any number of other systems may beincluded. Although an aerospace example is shown, the principles of themethods and systems described herein may be applied to other industries,such as the automotive industry.

Apparatus and methods embodied herein may be employed during any one ormore of the stages of the production and service method 100. Forexample, components or subassemblies corresponding to production process108 may be fabricated or manufactured in a manner similar to componentsor subassemblies produced while the aircraft 102 is in service. Also,one or more apparatus embodiments, method embodiments, or a combinationthereof may be utilized during the production stages 108 and 110, forexample, by substantially expediting assembly of or reducing the cost ofan aircraft 102. Similarly, one or more of apparatus embodiments, methodembodiments, or a combination thereof may be utilized while the aircraft102 is in service, for example and without limitation, to maintenanceand service 116.

FIG. 4 is an exemplary embodiment of a system 200 for inductionprocessing of a composite material. In the exemplary embodiment, system200 includes a first power supply 210, a second power supply 212, athird power supply 214, and a fourth power supply 216. In the exemplaryembodiment, system 200 also includes a plurality of individual inductionheating coils, such as, a first coil 220, a second coil 222, a thirdcoil 224, a fourth coil 226, a fifth coil 228, a sixth coil 230, aseventh coil 232, an eighth coil 234, a ninth coil 236, a tenth coil238, an eleventh coil 240, and a twelfth coil 242. Each of coils 220,222, 224, 226, 228, 230, 232, 234, 236, 238, 240, and 242 include atleast one winding and a coil element (not shown in FIG. 4). Coils 220,222, 224, 226, 228, 230, 232, 234, 236, 238, 240, and 242 are positionedto define a process area 244. A work piece 246 placed within processarea 244 is provided with electromagnetic fields that facilitateinductive heating of the work piece 246. In the exemplary embodiment,the work piece 246 includes a thermoplastic material 248 and a tool 250.In some embodiments, the tool 250 is cast from, for example, fusedsilica. In some examples, fused silica tooling may be formed fromThermo-Sil® Castablc 120, available from Thermo Materials Corporation ofLinden, N.J.

In some embodiments, tool 250 may also be a laminated tool typicallymade up of layers of, for example, austenitic stainless steel. Also, insome embodiments, tool 250 includes a susceptor 252, for example, ametal susceptor. Susceptor 252 may also be embedded within thermoplasticmaterial 248. Although specifically described herein as including twelveinduction heating coils and four power supplies, system 200 may includeany number of induction heating coils and any number of power suppliesthat facilitate system 200 functioning as described herein.

In the exemplary embodiment, first power supply 210 is coupled to, andconfigured to control a supply of electricity provided to, first coil220, third coil 224, and fifth coil 228. Similarly, second power supply212 is coupled to, and configured to control a supply of electricityprovided to, seventh coil 232, ninth coil 236, and eleventh coil 240. Inthe exemplary embodiment, third power supply 214 is coupled to, andconfigured to control a supply of electricity provided to, second coil222, fourth coil 226, and sixth coil 230. Similarly, fourth power supply216 is coupled to, and configured to control a supply of electricityprovided to, eighth coil 234, tenth coil 238, and twelfth coil 242.

The use of multiple power supplies 210, 212, 214, and 216 facilitateseven heating of a large work piece, for example, work piece 246, withoutthe impractically high voltages that would be required from a singlepower supply to power a single coil large enough to heat work piece 246or to power multiple coils that define a process area (e.g., processarea 244) large enough to heat work piece 246. In some exemplaryembodiments, work piece 246 is greater than forty meters in length.

FIG. 5 is a block diagram of work piece 246 positioned within processarea 244. As described above, process area 244 is defined by multiplecoils, for example, coils 220, 222, 224, 226, 228, and 230. Sizes ofcoils 220, 222, 224, 226, 228, and 230 are dependent upon factors suchas, but not limited to, a frequency of AC current oscillation, a numberof coil turns, a plan form dimension of the coil, a process temperature,and a resistivity of susceptor 252. In the exemplary embodiment, thefrequency of AC current oscillation is in the range of 500 Hz to 5000Hz.

In at least one example, work piece 246 has a width 254 of four feet ina y-direction 256 and a length 258 of sixteen feet in an x-direction260. Six coils 220, 222, 224, 226, 228, and 230, each have a width 262of three feet and are oriented to define an eighteen foot long processarea 244. In the example of FIG. 5, first power supply 210 and thirdpower supply 214 supply electricity to coils 220, 222, 224, 226, 228,and 230. Since each of coils 220, 222, 224, 226, 228, and 230 provideapproximately twelve square feet of coverage along process area 244, andeach of power supplies 210 and 214 supply three coils with electricity,each of power supplies 210 and 214 provides thirty-six square feet ofcoverage along process area 244. In the exemplary embodiment, the areaof work piece 246 heated by each individual power supply is kept to apredetermined number. In the example above, the area heated by eachindividual power supply is kept to thirty-six square feet per powersupply. More specifically, to heat a different sized work piece 246, thedimensions of coils 220, 222, 224, 226, 228, and 230 may be changed. Forexample, to heat work piece 246 having width 254 of eight feet andlength 258 of sixteen feet, twelve coils (not shown in FIG. 5, however,aligned in the same manner as coils 220, 222, 224, 226, 228, and 230)each having width 262 of one and a half feet are oriented to define asixteen feet long process area 244. Four power supplies (not shown inFIG. 5) are used to provide electricity to the twelve coils. Thedimensions of the coils are selected to maintain the predeterminedheating area per power supply while configuring system 200 to heat adifferent sized work piece 246.

However, by way of non-limiting example, if first coil 220 is suppliedwith electricity having a different phase than the electricity suppliedto second coil 222, electromagnetic fields (shown in FIG. 5) produced byfirst coil 220 may interfere with electromagnetic fields (shown in FIG.6) produced by second coil 222. More specifically, if supplied withelectricity having different phases, electromagnetic fields (shown inFIG. 5) produced by first coil 220 may cancel electromagnetic fields(shown in FIG. 6) produced by second coil 222, resulting in unevenheating of the work piece. In other words, individual coils 220, 222,224, 226, 228, 230, 232, 234, 236, 238, 240, and 242 positioned adjacentto one another may produce suboptimal heating of the work piece due toelectromagnetic interference.

FIG. 6 is an expanded diagram of a portion of the exemplary embodimentof system 200 shown in FIG. 4. As shown in FIG. 4, system 200 includesfirst coil 220, second coil 222, and third coil 224. First coil 220 andthird coil 224 are coupled to first power supply 210. Third coil 224 iscoupled to third power supply 214. Electromagnetic fields 270 and 272are produced by first coil 220 and third coil 224, respectively, whenfirst coil 220 and third coil 224 are energized by first power supply210.

FIG. 7 is an expanded diagram of the portion of the exemplary embodimentof system 200 shown in FIG. 6. An electromagnetic field 274 is producedby second coil 222 when second coil 222 is energized by third powersupply 214.

In the exemplary embodiment, system 200 (shown in FIGS. 4, 5, and 6)facilitates reducing electromagnetic interference between adjacent coilsby selectively energizing coils 220, 222, 224, 226, 228, 230, 232, 234,236, 238, 240, and 242. In other words, use of multiple individual coils220, 222, 224, 226, 228, 230, 232, 234, 236, 238, 240, and 242positioned adjacent to one another to define process area 244facilitates energizing adjacent coils at different times. The coils 220,222, 224, 226, 228, 230, 232, 234, 236, 238, 240, and 242 arealternately turned “on” and “off” to ensure the electromagnetic field270 produced by one coil does not adversely affect the electromagneticfield 274 produced by an adjacent coil. For example, in the exemplaryembodiment, first power supply 210 provides electricity to coils 220,224, and 228 at times when third power supply 214 is not providingelectricity to coils 222, 226, and 230. The timing of supplyingelectricity to coils 220, 222, 224, 226, and 228 facilitates reducingelectromagnetic interference between electromagnetic fields 270, 272,and 274 (shown in FIGS. 6 and 7). Additionally, third power supply 214provides electricity to coils 222, 226, and 230 at times when firstpower supply 210 is not providing electricity to coils 220, 224, and228. Second and third power supplies 212 and 216 operate in the samemanner.

Similarly, in the exemplary embodiment, third power supply 214 providespower to coils 222, 226, and 230 at alternate times than second powersupply 212 provides power to coils 232, 236, and 240 in order to preventelectromagnetic interference between coils 230 and 232. In the exemplaryembodiment, prevention of interference between the electromagneticfields produced by coils 230 and 232 may be facilitated by configuringfirst power supply 210 and second power supply 212 to turn thecorresponding coils “on” and “off” at the same time, and configuringthird power supply 214 and fourth power supply 216 to turn thecorresponding coils “on” and “off” opposite to first and second powersupplies 210 and 212.

The above described control scheme for powering coils 220, 222, 224,226, 228, 230, 232, 234, 236, 238, 240, and 242 facilitates driving thetemperature of a smart susceptor, for example, susceptor 252, and thepart up to the Curie point of the susceptor 252 and holding thetemperature so consolidation can occur. Various system configurations,including, varying the number of turns versus the number of coils versusthe number of power supplies, changing frequencies and/or susceptorthicknesses, and varying the lengths of time of each power supply isheld “on” and “off,” may be combined to create the desired processingcapability. In an example embodiment, first and second power supplies210 and 212 provide electricity to the corresponding coils forapproximately one-half second to ten seconds and do not provideelectricity to the corresponding coils for approximately one to tenseconds. In another exemplary embodiment, first and second powersupplies 210 and 212 provide electricity for approximately one-halfsecond to thirty seconds and do not provide electricity for one tothirty seconds. As described above, when first and second power supplies210 and 212 are not powering coils 220, 224, 228, 232, 236, and 240,third and fourth power supplies 214 and 216 are powering coils 222, 226,230, 234, 238, and 242, and vice versa. The time ranges above are givenas examples only, and any time ranges may be used that allow system 200to function as described herein.

FIG. 8 is a flowchart 300 of an exemplary method for production ofthermoplastic components using induction heating. The exemplary methodincludes positioning 302 a plurality of induction heating coils todefine a process area for a thermoplastic component. The plurality ofinduction heating coils includes a first set of coils and a second setof coils. The exemplary method also includes controlling 304 a supply ofelectricity provided to the plurality of inductive heating coils tointermittently activate the coils to facilitate prevention ofelectromagnetic interference between adjacent coils. Positioning 302 theplurality of induction heating coils further includes positioning theplurality of coils such that coils of the first set of coils and coilsof the second set of coils alternate along the length of the processarea.

Controlling 304 the supply of electricity provided to the plurality ofinduction heating coils further includes controlling a supply of powerprovided to the first set of coils independently from the supply ofpower provided to the second set of coils. The first set of coils aresupplied with power when power is not supplied to the second set ofcoils, and power is provided to the second set of coils when power isnot provided to the first set of coils. As described above, a firstpower supply provides electricity to the first set of coils and a secondpower supply provided electricity to the second set of coils.

The above described system of positioning individual coils in sequenceand connecting them to a set of independent power supplies that canenergize individual coils (or sets of coils), allows the coil sizes toremain relatively small compared to the size of the components to beproduced. Furthermore, the above described system facilitates rapidfabrication of large composite structures to meet accelerated productionrates without increasing a number of apparatuses and tooling. Inductionheating with susceptors, in combination with the above described systemof supplying electromagnetic fields to the susceptors, reduces theextended thermal cycle inherent in standard autoclave processingsystems.

The above described induction consolidation system eliminates the needto heat the tool, which facilitates rapid heating and cooling cycleswhile maintaining a consistent and controlled processing temperature. Byeliminating the long heating and cooling cycles typical of the autoclavecycles, a rate insensitive process for large scale thermoplasticcomposite structures is facilitated.

The above described system enables the application of inductionprocessing to the consolidation of large thermoplastic compositecomponents such as wing skins and wind turbine blades. In addition, itenables the utilization of higher performing thermoplastic resins and arapid method for fabricating these components, which facilitatesreducing the large inventory and capital issues associated withautoclave production.

The above described system provides a cost effective solution forconsolidation of large thermoplastic composite structures that enablesimproved performance and cost savings. Furthermore, the above describedsystem facilitates fabrication of large thermoplastic components withoutthe use of traditional fasteners, which reduces a component count. Theuse of induction heating facilitates a reduction in surface preparation,in many cases, necessitating only a solvent wipe to remove surfacecontaminants. Furthermore, the above described system facilitates: useof materials that have an indefinite shelf life at room temperature,short process cycle time (e.g., typically measured in minutes), enhancedjoint performance, especially hot/wet and durability, and rapid fieldrepair of composites or other structures. In addition, componentsfabricated using the above described system show little or no loss ofbond strength after prolonged exposure to environmental influences.

Exemplary embodiments of systems and methods for fabricatingthermoplastic components using induction heating are described above indetail. The systems and methods are not limited to the specificembodiments described herein, but rather, components of systems and/orsteps of the method may be utilized independently and separately fromother components and/or steps described herein. The exemplaryembodiments can be implemented and utilized in connection with otherfabrication applications.

This written description uses examples to disclose the embodiments,including the best mode, and also to enable any person skilled in theart to practice the embodiments, including making and using any devicesor systems and performing any incorporated methods. The patentable scopeof the disclosure is defined by the claims, and may include otherexamples that occur to those skilled in the art. Such other examples areintended to be within the scope of the claims if they have structuralelements that do not differ from the literal language of the claims, orif they include equivalent structural elements with insubstantialdifferences from the literal languages of the claims.

What is claimed is:
 1. A method of fabricating a thermoplastic componentusing inductive heating, said method comprising: forming a workpiececomprising the thermoplastic component and a susceptor; placing thethermoplastic component and the susceptor between a top tool and abottom tool, wherein the top tool and the bottom tool comprise fusedsilica or stainless steel; positioning a plurality of induction heatingcoils to define a process area for passage of the thermoplasticcomponent, wherein the plurality of induction heating coils comprises afirst set of coils and a second set of coils, wherein individual coilsof the second set of coils are positioned between a pair of individualcoils of the first set of coils; configuring a first power supply toprovide the first set of coils with electricity for a firstpredetermined period of time while a second power supply is notsupplying electricity to the second set of coils; configuring the secondpower supply to provide the second set of coils with electricity for asecond predetermined period of time when the first power supply is notproviding electricity to the first set of coils; controlling a supply ofelectricity provided to the plurality of induction heating coils tointermittently activate the first set of coils and the second set ofcoils by alternating the supply of electricity between the first powersupply and the second power supply so that the first set of coils isprovided with electricity when electricity is not provided to the secondset of coils, and the second set of coils is provided with electricitywhen electricity is not provided to the first set of coils wherein theprocess area extends through the first set of coils and the second setof coils, wherein the first power supply and the second power supply areconfigured to alternately power the first set of coils and the secondset of coils such that the first set of coils and the second set ofcoils are energized at different times to reduce electromagneticinterference between individual coils of the first set of coils and thesecond set of coils; and passing the workpiece through the process area,wherein the process area extends through the first set of coils and thesecond set of coils.
 2. The method in accordance with claim 1, whereincontrolling the supply of electricity provided to the plurality ofinduction heating coils further comprises controlling the supply ofelectricity provided to the first set of coils independently from thesupply of electricity provided to the second set of coils.
 3. The methodin accordance with claim 1, wherein controlling the supply ofelectricity provided to the plurality of induction heating coils furthercomprises configuring the first power supply to power the first set ofcoils and configuring the second power supply to power the second set ofcoils.
 4. The method of claim 1, wherein the thermoplastic component isa wing skin.
 5. The method of claim 4, wherein the wing skin isfabricated with only a solvent wipe to remove surface contaminants. 6.The method of claim 4, wherein the method further comprises repairingthe wing skin in the process area.
 7. The method of claim 1, wherein thethermoplastic component is a wind turbine blade.
 8. The method of claim7, wherein the wind turbine blade is fabricated without fasteners. 9.The method of claim 7, wherein the wind turbine blade is fabricated withonly a solvent wipe to remove surface contaminants.
 10. The method ofclaim 7, wherein the method further comprises repairing the wind turbineblade in the process area.
 11. A method for fabricating a thermoplasticcomponent using inductive heating, said method for use in aircraftmanufacturing, said method comprising: forming a workpiece comprisingthe thermoplastic component and a susceptor; placing the thermoplasticcomponent and the susceptor between a top tool and a bottom tool,wherein the top tool and the bottom tool comprise fused silica orstainless steel; positioning at least a first set of coils and a secondset of coils to define a process area for passage of the thermoplasticcomponent, wherein first coils of the first set of coils and secondcoils of the second set of coils alternate along a length of the processarea; configuring a first power supply to provide electricity to thefirst set of coils; and configuring a second power supply to provideelectricity to the second set of coils, wherein the first power supplyis configured to provide electricity to the first set of coils for afirst predetermined period of time when the second power supply is notproviding electricity to the second set of coils, and the second powersupply is configured to provide electricity to the second set of coilsfor a second predetermined period of time when the first power supply isnot providing electricity to the first set of coils in order to reduceelectromagnetic interference between the first set of coils and thesecond set of coils, wherein the first power supply and the second powersupply are configured to alternately power the first set of coils andthe second set of coils such that the first set of coils and the secondset of coils are energized at different times to reduce electromagneticinterference between individual coils of the first set of coils and thesecond set of coils; and passing the workpiece through the process area,wherein the process area extends through the first set of coils and thesecond set of coils.
 12. The method of claim 4, wherein the wing skin isfabricated without fasteners.
 13. The method of claim 11, wherein thethermoplastic component is a wing skin.
 14. The method of claim 13,wherein the wing skin is fabricated without fasteners.
 15. The method ofclaim 13, wherein the wing skin is fabricated with only a solvent wipeto remove surface contaminants.
 16. The method of claim 13, wherein themethod further comprises repairing the wing skin in the process area.17. The method of claim 11, wherein the thermoplastic component is awind turbine blade.
 18. The method of claim 17, wherein the wind turbineblade is fabricated without fasteners.
 19. The method of claim 17,wherein the wind turbine blade is fabricated with only a solvent wipe toremove surface contaminants.
 20. The method of claim 17, wherein themethod further comprises repairing the wind turbine blade in the processarea.